Deadline iosched: Fix batching fairness
authorAaron Carroll <aaronc@gelato.unsw.edu.au>
Tue, 30 Oct 2007 09:40:13 +0000 (10:40 +0100)
committerJens Axboe <axboe@carl.home.kernel.dk>
Fri, 2 Nov 2007 07:47:25 +0000 (08:47 +0100)
commit6f5d8aa6382eef2b26032c88656270bdae7f0c42
tree6ee855ce6e8b0eb8cb04d41579ac11cb25a92759
parentdfb3d72a9aa519672c9ae06f0d2f93eccb35482f
Deadline iosched: Fix batching fairness

After switching data directions, deadline always starts the next batch
from the lowest-sector request.  This gives excessive deadline expiries
and large latency and throughput disparity between high- and low-sector
requests; an order of magnitude in some tests.

This patch changes the batching behaviour so new batches start from the
request whose expiry is earliest.

Signed-off-by: Aaron Carroll <aaronc@gelato.unsw.edu.au>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
block/deadline-iosched.c